Week 6
Embryology - 1 Dec 2023    Expand to Translate
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Key Events of Human Development during the sixth week (week 6) following fertilization or clinical gestational age GA week 8 (LMP).
This week corresponds to Carnegie stages 16 and 17.
| Week 6 Links: stage 16 | stage 17 | Lecture - Head | Outflow Tract | Category:Week 6 | GA week 8 |
Carnegie Stages
| Week: | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| Carnegie stage: | 1 2 3 4 | 5 6 | 7 8 9 | 10 11 12 13 | 14 15 | 16 17 | 18 19 | 20 21 22 23 |
Historic Carnegie Stages 16 and 17.
Timeline
| Week 6 - Human Embryo Stages and Events (GA week 8) | ||
|---|---|---|
| Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9 | ||
| Event | ||
| Pituitary - Week 6 connecting stalk between pouch and oral cavity degenerates
Parathyroid - Week 6 diverticulum elongate, hollow then solid, dorsal cell proliferation Thymus - Week 6 diverticulum elongate, hollow then solid, ventral cell proliferation Adrenal - Week 6 fetal cortex forms from mesothelium adjacent to dorsal mesentery, medulla neural crest cells from adjacent sympathetic ganglia Respire - Week 6 - descent of heart and lungs into thorax. Pleuroperitoneal foramen closes Tongue Week 6 - gustatory papilla, caudal midline near the foramen caecum (week 6 to 7 - nerve fibers approach the lingual epithelium) | ||
| Stage 16 |  Limbs upper limb bud nerves median nerve, radial nerve and ulnar nerve entered into hand plate, myoblasts spindle shaped and oriented parallel to limb bud axis. Heart - outflow tract elliptical configuration with four cushions, the two larger fusing at this stage. Semilunar valve leaflets form at the downstream end of the cushions Head lip and palate components of the upper lip, medial nasal prominence and maxillary process present, median palatine process appears. | |
| Stage 17 |  Neural - telencephalon areas of the future archicortex, paleocortex, and neocortex, visible. Beginning of future choroid plexus[2] Sense - Smell olfactory nerve fibres enter the brain[3] Neural - primordium of the epidural space appears first on the ventral part of the vertebral canal and develops rostro-caudally[4] Pancreas - rotation of the developing stomach moves ventral bud dorsally and fuses with the dorsal bud. | |
| Heart - separation of common cardiac outflow (aortic arch and pulmonary aorta) | ||
| Note - the day timing of stages is only approximate, system names link to first page of that specific system, and events are based upon the literature cited below. | ||
| References | ||
| Event | ||
| pituitary - Week 6 connecting stalk between pouch and oral cavity degenerates
parathyroid - Week 6 diverticulum elongate, hollow then solid, dorsal cell proliferation thymus - Week 6 diverticulum elongate, hollow then solid, ventral cell proliferation adrenal - Week 6 fetal cortex forms from mesothelium adjacent to dorsal mesentery, medulla neural crest cells from adjacent sympathetic ganglia respiratory - Week 6 - descent of heart and lungs into thorax. Pleuroperitoneal foramen closes tongue Week 6 - gustatory papilla, caudal midline near the foramen caecum (week 6 to 7 - nerve fibers approach the lingual epithelium) | ||
| Stage 16 | neural - first parasympathetic ganglia, submandibular and ciliary, are identifiable[1]
limb upper limb bud nerves median nerve, radial nerve and ulnar nerve entered into hand plate, myoblasts spindle shaped and oriented parallel to limb bud axis. heart - outflow tract elliptical configuration with four cushions, the two larger fusing at this stage. Semilunar valve leaflets form at the downstream end of the cushions head lip and palate components of the upper lip, medial nasal prominence and maxillary process present, median palatine process appears. | |
| Stage 17 |
neural - telencephalon areas of the future archicortex, paleocortex, and neocortex, visible. Beginning of future choroid plexus[2] smell olfactory nerve fibres enter the brain[3] neural - primordium of the epidural space appears first on the ventral part of the vertebral canal and develops rostro-caudally[4] pancreas - rotation of the developing stomach moves ventral bud dorsally and fuses with the dorsal bud. | |
| heart - separation of common cardiac outflow (aortic arch and pulmonary aorta) |
References
- ↑ Müller F & O'Rahilly R. (1989). The human brain at stage 16, including the initial evagination of the neurohypophysis. Anat. Embryol. , 179, 551-69. PMID: 2751117
- ↑ Müller F & O'Rahilly R. (1989). The human brain at stage 17, including the appearance of the future olfactory bulb and the first amygdaloid nuclei. Anat. Embryol. , 180, 353-69. PMID: 2802187
- ↑ <pubmed>15604533</pubmed>
- ↑ Patelska-Banaszewska M & Woźniak W. (2004). The development of the epidural space in human embryos. Folia Morphol. (Warsz) , 63, 273-9. PMID: 15478101
Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
- Carnegie Stages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Stages | Timeline
Glossary Links
- Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link
Cite this page: Hill, M.A. (2023, December 1) Embryology Week 6. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Week_6
- © Dr Mark Hill 2023, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
